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H. L. M. J. BENARD.

AERIAL SIGNAL LIGHT.

APPLICATION FILED MAY 23. 919.

Patented July 12, 1921.

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AERIAL SIGNAL LIGHT. v APPLICATION FILED MAY 23, 1919.

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3 SHEETS-SHEET 3- UNITED STATES HENRI LUG-LIEN MARIE JOSEPH BENARD, OFPARIS, FRANCE.

AERIAL SIGNAL-LIGHT.

Specification of Letters Patent. Patented July 12, 1921,

Application filed May 23, 1919. Serial No. 299,104.

T 0 all whom it may concern:

Be it known that I, HENRI LUGLIEN MARIE JosnrH Biiimmi, a citizen of theRepublic of should be able to illuminate in a continuous manner, fromthe horizon to the zenith of the search-light. It is notnecessary thatthe intensity of the beam shall be equal in all parts of the verticalplane. Rationally speaking the beam of light should have its maximumintensity in the horizontal direction and this intensity shouldgradually decrease from the horizon to a point above the Searchlight inwhich latter region it need only have suiiicient intensity to enable thelight to be visible at the greatest altitude which can be obtained byaircraft. As this altitude does not, in practice, exceed 4000 meters avery low intensity is suflicient for the light to be visible, the moreso since at high elevations visibility is very good owing to the purityof the air.

The searchlight forming-the subject of this invention complies in allrespects with the above conditions.

In principle the invention is characterized by the provision, inconnection with a searchlight, of an aperture or window by means ofwhich it is possible to illuminate from the horizon to the zenith of theSearchlight in a continuous manner and with a single source of light.

In the accompanying drawing, Figure 1 is a vertical section of asea-rchlight constructed according to the invention. Fig. 2 isa frontview of the optical panel ofthe searchlight. Fig. 3 shows a modificationand Fig. 4 is a curve showing the ranges of the beam of lightof-theSearchlight.

Referring to'Fig. l, the Searchlight-consists essentially of an opticalpanel 1, composed of dioptric and catadioptric' elements. 2 designates asource of light, in this case anincandescent mantle, but any othersource of light could be employed. table 3 supporting the optical systemcarries a crown wheel 4 meshing with the pinion 5 of a motor.

The prismatic elements are arranged so as to concentrate the luminousrays emitted by the source of light 2 into a very intense beam limited,on the one hand, by the line AB which is horizontal, and on the otherhand by the line CD, which forms withtthe orizontal a certain angle awhich is determined by practical considerations.

The light source is at the focus of the optical panel 1, and in thecenter of the portion of the panel situated above the horizontal planePF passing through the light source, i ig. 2, the prisms are supportedby a double standard M having an interval or 'gap E which forms anaperture or window in which there are no prisms. If reference is had toFig.- 1, it will be seen that the rays emitted by the source of lightpass through this interval and give illumination from the horizontal upto the vertical line passing through the axis of the Searchlight.

The interval E is dimensioned in such a manner that the pencil of lightformed by the direct light emitted by the source is of horizontalamplitude equal to that of the pencil formed by the prisms and retainsthe same character in the whole vertical plane.

It should be noted that the horizontal amplitude of the pencil given bythe prisms being very small, the interval E is very small and,consequently, the small quantity of prisms removed from the panel onlyinapprc-ciably diminishes the intensity of the beam or pencil.

The total beam obtained stretches therefore in a vertical plane from thehorizon to the vertical passing through the axis of the searchlight, andthis without interruption of continuity.

If the curves of the ranges of the beam were traced, one would obtain,for the whole beam, the curve represented in Fig. 4 in which 2represents the searchlight. The shaded zone included in the angle acorresponds to the intensity of the beam of light given out by theoptical panel 1. The shaded zone included in the angle (5 corresponds tothe intensity of the beam of light emitted directly by the source.

It will therefore be seen that, taking by way of example an altitude of4000 meters to which an aeroplane can rise, this altitude beingindicated by athe lowest point of the beam, the aviator will always bewithin the beam of light, subject of course to the condition that he isnot situated at a distance from the Searchlight which is superior to thehorizontal range of this latter.

The apparatus shown in Figs. 1 and 2 gives a simple flash. It is obviousthat it would be posslble to construct searchlights having a pluralityof regular panels or grouped around the source of light and thus to haveeither simple flashes or groups of flashes. i

It would also be possible to construct a searchlight composed ofreflectors alone or of reflectors and lenses, as shown in Fig. 3. In theupper portion of each reflector A and in the upper half of each lens Lis formed a window which allows the light emitted by the source placedat the focus to escape directly, as in the device shown in Figs. 1 and.2.

Claims: 5

1. A signal light for use in aerial navigation, comprising incombination a source of light, an optical system for projecting the beamfrom said source, said optical system having a narrow central apertureextending from a horizontal plane passing through the light source tothe zenith.

2. A signal light for use in aerial navigaments, said standard having anaperture de-- void of optical elements extending from the horizon to thezenith.

4. A signal light for use in aerial naviga tion comprising incombination a source of l ght, means for pro ect1ng the beam from saidsource substantially horizontally, a central narrow window beingprovided extending from the horizon-to the zenith for the passage of aportion of the light emitted by I said source.

HENRI LUGLIENMARIE JOSEPH BENARD

